1. Field of the Invention
This invention relates to a thixotropic, water based general purpose, polyvinyl alcohol adhesive gel for porous and semiporous substrates such as paper, card board, cloth and wood.
2. Background Art
Many different general purpose adhesives are available for adhering porous and semiporous substrates such as paper. However, such adhesives have shortcomings for use in projects which are performed on wall boards and other vertical surfaces such as in a class room by young children.
The gels of this invention contain water, polyvinyl alcohol, and xanthan gum within certain proportions so as to provide viscosities and a thixotropic index within certain ranges. Optionally, the gel includes a diphenyl methane dye to provide color to the gel. Preferably, the gel consists essentially of: water; a partially hydrolyzed polyvinyl alcohol; xanthan gum; a water-soluble defoamer; and a water-soluble plasticizer for the polyvinyl alcohol which does not destroy the clarity of the gel. Optionally, other ingredients can be added which do not destroy the advantageous properties of the gel. Compatible preservatives and dyes are generally added to the gel.
Our copending applications Ser. No. 07/976,553 filed Nov. 16, 1992 and its divisional 08/150,435 filed on Nov. 10, 1993, both of which are incorporated herein in their entirety by reference, relate to clear, thixotropic aqueous adhesive gels containing water, partially hydrolyzed polyvinyl alcohol, various polymeric thickening agents such as about 0.5% to 1.5% of xanthan gum, colorants, a water soluble plasticizer for the polyvinyl alcohol, and a defoamer. Our copending application Ser. No. 08/077,023 filed on Jun. 15, 1993, which is also incorporated herein in its entirety by reference, relates to an aqueous thixotropic adhesive gel containing water, polyvinyl acetate, polyvinyl alcohol, wood flour, glyoxal, and xanthan gum as the thickening agent.
Applicants have found that smaller quantities of the xanthan gum from that recited in their copending applications filed on Nov. 16, 1992 and Nov. 10, 1993 are operable and the color of water soluble triphenyl methane dyes in the gels of these copending cases has better stability in sunlight when xanthan gum is used in comparison to the use of the sodium salt of carboxymethylcellulose (CMC) which is the preferred gum in these copending cases.